The reason we don't have 360 or PS3 emulators, yet, is because there's barely any info out there about them and it's simply a tremendous boring amount of work of coding.
Some people have actually coded SPE emulators, idk if this has been done for the main PPC as well though. and there's at least IBM's cell simulator.
Anyway, that's not the hardest part of emulation, it's just a f**king large amount of monotone work without which nothing of the hard stuff can even be started (and doing boring work just for being able to do hard work is kinda discouraging

).
The Wii 2 won't be emulated in Dolphin because it most likely will differ in about EVERY aspect to the GC/Wii:
- CPU JIT probably needs to be rewritten, I doubt there will be THAT many common areas to the current code
- The Wii 2 will have a programmable GPU pipeline rather than the fixed-function pipeline of the Flipper/Hollywood. If it is really based on an r700 chip, it might be comparatively easy to emulate since ATI has published numerous register docs on their GPUs. Anyway, emulating THAT GPU would require compeletely separate graphics emulation code
- The Wii 2 will probably have a revamped security architecture (I guess Nintendo won't like getting hacked that hard again). Guess we can screw over our whole IOS high level emulation code as well then.
- Will have a new input system, so screw over our whole Wiimote emulation as well
- too lazy to think further, but I guess there's plenty other stuff to mention...
Generally speaking, in contrast to GC->Wii (which was merely an incremental change, raising clock speeds, adding the starlet, adding wiimotes, adding WiFi, etc), Wii->Wii2 will be a radical change in most, if not all, subsystems of the hardware. Again, emulating the Wii 2 inside Dolphin would be the same like emulating the 360 in Dolphin.
On top of that, by the time the Wii 2 gets hacked, documented, a compiler chain gets created and homebrew for testing arises, Dolphin development will have ceased to almost-no-progress anyway
